This invention relates to magnesium reduced titanium tetrahalide catalyst systems.
It is known to reduce titanium tetrahalides with Grignard reagents, that is, RMgX compounds produced by reacting magnesium and an organic halide in the presence of ether. It is also known to produce what is termed in the art a "solventless" Grignard, which is produced by reacting magnesium metal with an organic halide in the presence of a solvent which is designated as a nonsolvating solvent (i.e., an inert noncomplexing diluent) such as a noncomplexing hydrocarbon as distinguished from an ether. True Grignard reagents, as a practical matter, present serious problems as reducing agents in the production of catalysts in view of the difficulty in removing the large amount of ether and the remaining complexed ether can reduce the effectiveness of olefin polymerization catalyst systems prepared with the thus treated Grignard reagent.
With olefin polymerization, particularly the polymerization of ethylene or predominantly ethylene-containing olefin mixtures, it has been found to be more economical to carry out the polymerization at a temperature low enough that the resulting polymer does not go into solution in the liquid diluent used, and to recover the polymer without elaborate catalyst removal steps. This results in residual catalyst remaining in the polymer and thus requires high productivity rates in order to be practical.